The present invention is a process for substituting cycloalkyl substituents for a silicon bound hydrogen of a silane. The process employs an organoborane compound as a catalyst to increase the apparent rate of the reaction and to increase the yield of desired cycloalkyl substituted silanes.
Barry, U.S. Pat. No. 2,626,266, issued Jan. 20, 1953, describes a process where a benzenoid hydrocarbon is reacted with trichlorosilane in the presence of a boron halide, at a temperature above 230.degree. C., and under sufficient pressure that at least a portion of the reaction mixture is in a condensed phase. Under these conditions, aromatic halosilanes are reported to constitute a major portion of the reaction product. Barry discloses that the boron halide may be added in the form of boron trichloride or trifluoride, or it may by produced in situ by the addition of a material such as boric acid. Typical reaction times for the process were 16 to 17 hours.
Barry, U.S. Pat. No. 2,572,302. issued Oct. 23. 1951, describes a process where an organodichloromono-hydrosilane, for example methyldichlorosilane, is reacted with benzene in the presence of a boron halide, at a temperature above 150.degree. C. and under sufficient pressure that at least a portion of the reaction mixture is in a condensed phase. Under these conditions, the organodichlorosilyl derivatives of the hydrocarbon are reported to constitute a major portion of the reaction product. Barry discloses that the boron halide may be added in the form of boron trichloride or trifluoride, or it may be produced in situ by the addition of materials such as boric acid. A typical reaction time for the process was 26 hours.
Brewer. U.S. Pat. No. 2,594,860, issued Apr. 29. 1952. describes a process for making phenyltrichlorosilane by reacting a mixture comprising benzene, dichlorosilane, and silicon tetrachloride in the presence of a boron halide as a catalyst. Brewer states that the reaction is preferably conducted in a pressure reactor, under 750 psi to 2500 psi pressure, at temperatures ranging from about 250.degree. C. to below the decomposition point of either the reactants or the reaction product. Brewer discloses that the boron halide can be boron trichloride or boron trifluoride or its etherate. The reported time for the reaction was four hours.
Wagner, U.S. Pat. No. 2,775,606, issued Dec. 25, 1956, describes a process where benzene is reacted with a mixture of dichlorosilane and trichlorosilane to produce a product which is principally phenyldichlorosilane. The preferred pressure range for the process is 1,000 psi to 4,000 psi and the preferred temperature range is 300.degree. C. to 500.degree. C. Wagner states that the use of a catalyst results in a decreased reaction time and permits a rapid flow process. Contact times of 2-12 hours are reported for the static process and a calculated contact time of about one minute for a rapid flow process. Wagner reports Lewis acid catalysts of the metal halide type such as BCl.sub.3, CbCl.sub.5, and AlCl.sub.3 to be effective in the process.
Brewer. U.S. Pat. No. 2,600,198 issued Jun. 10, 1952, described a process where an aromatic hydrocarbon and a halosilane, containing at least one silicon-bonded hydrogen, are reacted in the presence of a Friedel-Crafts type catalyst, for example trichloroboron. Brewer states that if product silane is removed along with substantially all the evolved hydrogen and to the residue is added an additional amount of aromatic hydrocarbon and halosilane, the newly added reactants are again caused to react and that a greatly increased conversion of the newly added reactants to aromatic halosilanes can be realized. Brewer states that under the described conditions the reaction can be effected in about 3 to 30 minutes.
Wright, Journal of Organometallic Chemistry, 145: 307-314 (1978), reported on studies to determine the role of boron trichloride in the synthesis of phenyltrichlorosilane from benzene and trichlorosilane. Wright concluded that phenylboranes play an important role in the catalyst and that the reduction of boron trichloride was a slow process accounting for the induction period observed in the reaction of benzene with trichlorosilane.
Shafer, et al., U.S. Pat. No. 2,660,597 issued Nov. 24, 1953, describes the reaction of trichlorosilane with cyclohexane in the presence of boron trichloride catalyst. The reaction was run at 375.degree. C. for 14 hours. The reported yield for a six carbon atom alkyl chlorosilane was 13 weight percent.
The inventors have found that the presence of at least one organic substituent on boron compounds, described herein, provides a catalyst which can increase the apparent reaction rate and the product yield of the reaction of cycloalkanes with hydrogen containing halosilanes. The use of the organic substituted boron catalysts allows the process to be run at lower temperatures and shorter residence times, than those described by the above cited art. The shorter residence times and lower temperatures reduce undesirable reactions and the heat induced decomposition of reactants and products.